1. Field of the Invention
This invention resides in the area of bench trays that move over rollers in greenhouses and more particularly relates to a wire form bench tray having channels defined therein to carry both heat and/or water tubing.
2. Description of the Prior Art
Commercial greenhouses use tables or "benches" on which to grow plants. These benches keep the plants off the ground which higher location helps the plants avoid disease and allows for easier plant handling. The benches have metal frames supporting a series of support rollers, usually pipes. In the past the benches were made of wood or concrete until the mid-1970's when metal benches came into use. These flat planar metal benches were made of structural steel or aluminum tube framing with a wire mesh or diamond-shaped "expanded metal" surface. The openings in such bench surfaces allow for air circulation therethrough, reducing the humidity levels around the plants which drier conditions reduce some plant disease problems. Such benches supporting potted plants rest above the surface of the support roller pipes and are moved laterally by pushing the benches to move over the support roller pipes. Movement of the benches eliminates the need for establishing permanent walkways in a greenhouse as the benches can be moved aside to provide walk way openings where and when needed, thereby maximizing the surface area available for growing plants. The use of rolling benches in greenhouses can provide up to 20% more growing space in each greenhouse.
A problem with rolling bench trays is where to put the heat and/or water irrigation tubing. Earlier greenhouses used pipes carrying hot water or steam running under the benches. A common method of heating greenhouses today is the use of flexible tubing to carry hot water which tubing is disposed under the benches close to the plant roots. However, when a bench is moved, the plants thereon become moved out of alignment with the heat tubing which tubing remains stationary, resulting in uneven heating and significant waste of heat. Addressing this problem led to the common practice of today of placing flexible rubber tubing carrying hot water under, or on top of, the benches very close to the plants. If the heat tubing is placed under the bench tray, though, it does not move when the bench tray is moved. The heat tubing typically has a diameter of 0.25-0.75 inch and is positioned at 2-4 inch intervals running under the length of the bench tray. If the heat tubing is positioned on top of the bench tray, it interferes with the positioning of the plants and many plants cannot sit level.
The method of watering plants in greenhouses has also changed over the years. Watering by hand from a garden hose gave way to overhead spray booms which travel the length of the greenhouse. This method, in turn, was replaced by small irrigation tubing extending into each pot where the small tubes extend from a larger water tubing placed on the top of each bench.
Thus, a continuing problem with greenhouse benches has been where to put the heating and/or irrigation tubing so that they are not in the way of bench tray movement when rolling side to side or in the way of placing the maximum number of plants on the top of the bench tray. The heat and/or irrigation tubing when placed on the top of the bench tray often displace the pots, and heat may come in direct contact with a plant pot as the bench tray is moved which effect is undesirable. If the heat and/or irrigation tubing are placed under the bench tray, then the heat cannot move with the plants and will not be centered under the pots and no longer uniformly provide heat to the plants. Further, as mentioned above, heat and/or irrigation tubing placed under the benches can get in the way of support roller pipe movement when the bench is moved laterally on the support roller pipes from one position to another.